毛竹材性变异规律和解剖构造
发布时间：2019-06-09 16:30
【摘要】：竹材材性变异性大,快速检测竹材的物理力学性能并对其进行分级是竹产业发展的必然趋势。毛竹(Phyllostachys pubescens)是本文的主要研究对象,比较分析毛竹高度方向上几何尺寸的变化规律,对其进行分段研究。通过压痕法快速检测毛竹的压痕强度,探究压痕强度与竹材基本密度之间的相关性,验证能否用压痕法快速检测竹材的密度。分析不同压痕强度等级竹材维管束的微观结构特征和微纤丝角的大小,探讨维管束结构和微纤丝角的大小对竹材物理力学性能的影响机制。论文的主要研究结论如下:(1)以0.9 m及枝下高作为分割点,将毛竹分成三段,即:根部(砍伐处-0.9 m)、主干(0.9 m-枝下高)和稍部;并且0.9 m处的径级越大,毛竹的鲜重及体积越大。把0.9m处的径级作为主要指标,将0.9 m处的径级分成4个等级即:低径级:φ≤10 cm;中径级:10 cmφ≤12 cm;中高径级:12 cmφ≤14 cm;高径级:φ≥14 cm。(2)参照国内外标准,根据预试验的结果,在方便加工、确保有效测试次数、提高工作效率,避免试验过程出现偏心、受力不均等造成的劈裂现象的情况下,最终确定竹环的长度为20±0.5 mm,压辊直径为15 mm,压头形状是“十字型”,压入位移3 mm,确定竹环的压痕强度。(3)毛竹压痕强度与基本密度呈线性相关(R~2=0.8794)。毛竹株内压痕强度和基本密度差异性不显著,毛竹间压痕强度与基本密度差异性极显著。因此,用压痕法快速检测鲜竹的压痕强度是可行的,通过压痕强度与基本密度的关系式:y=0.0188x+0.1113可计算出毛竹的基本密度。参照AITC Grading Handbook for Laminating Lunber中E-rated Grades的分级方法,将压痕强度分成四个等级,根据每个等级压痕强度范围,可推测出毛竹基本密度的范围,为毛竹的定向利用提供数据支持。(4)不同压痕强度等级竹材的基本密度与顺纹抗压强度、抗弯弹性模量和抗弯强度都呈正相关,相关性显著。压痕强度与顺纹抗压强度、抗弯强度和抗弯弹性模量呈正相关,相关性显著。因此,利用压痕法快速检测鲜竹的力学性能,并对其进行分级是合理可行的。(5)维管束面积和纤维鞘面积随竹材基本密度的增加而增大,最大密度(0.71 g/cm~3)竹材的内方纤维鞘面积是最小密度(0.46 g/cm~3)竹材的3倍还多。不同密度竹材的内方纤维鞘的长、短轴随着密度的增加而增大。当密度大于0.61 g/cm~3时,随着密度增加纤维鞘长轴增加缓慢,纤维之间排列的密实程度也在增加,单根纤维显得小而密实,毛竹的力学性能随之增大。因此竹材维管束纤维鞘内的密实纤维决定着竹材的密度和力学性能。从竹青到竹黄毛竹微纤丝角的变化规律不明显,差异不显著。毛竹微纤丝角与压痕强度、抗弯强度和模量有显著的相关性。
[Abstract]:The variability of bamboo properties is great. It is an inevitable trend for the development of bamboo industry to quickly detect and classify the physical and mechanical properties of bamboo. Phyllostachys pubescens (Phyllostachys pubescens) is the main research object of this paper. The variation of geometric size in the height direction of Phyllostachys pubescens is compared and analyzed, and the segmented study is carried out. The indentation strength of Phyllostachys pubescens was detected quickly by indentation method, and the correlation between indentation strength and basic density of bamboo was explored to verify whether the indentation method could be used to detect the density of bamboo quickly. The microstructure characteristics and microfibril angle of bamboo vascular bundles with different indentation strength grades were analyzed, and the influence mechanism of vascular bundles structure and microfibrillar angle on the physical and mechanical properties of bamboo was discussed. The main conclusions of this paper are as follows: (1) using 0.9m and subbranch height as the dividing point, Phyllostachys pubescens is divided into three segments: root (cutting site-0.9 m), trunk (0.9m-branch height) and slightly); And the larger the diameter grade at 0.9 m, the larger the fresh weight and volume of Phyllostachys pubescens. Taking the diameter grade at 0.9m as the main index, the diameter grade at 0.9m is divided into four grades: low diameter grade: 蠁 鈮，
本文编号：2495704
[Abstract]:The variability of bamboo properties is great. It is an inevitable trend for the development of bamboo industry to quickly detect and classify the physical and mechanical properties of bamboo. Phyllostachys pubescens (Phyllostachys pubescens) is the main research object of this paper. The variation of geometric size in the height direction of Phyllostachys pubescens is compared and analyzed, and the segmented study is carried out. The indentation strength of Phyllostachys pubescens was detected quickly by indentation method, and the correlation between indentation strength and basic density of bamboo was explored to verify whether the indentation method could be used to detect the density of bamboo quickly. The microstructure characteristics and microfibril angle of bamboo vascular bundles with different indentation strength grades were analyzed, and the influence mechanism of vascular bundles structure and microfibrillar angle on the physical and mechanical properties of bamboo was discussed. The main conclusions of this paper are as follows: (1) using 0.9m and subbranch height as the dividing point, Phyllostachys pubescens is divided into three segments: root (cutting site-0.9 m), trunk (0.9m-branch height) and slightly); And the larger the diameter grade at 0.9 m, the larger the fresh weight and volume of Phyllostachys pubescens. Taking the diameter grade at 0.9m as the main index, the diameter grade at 0.9m is divided into four grades: low diameter grade: 蠁 鈮，
本文编号：2495704
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